correct imdb func name in docs

Author: zsdonghao

docs/modules/files.rst

@@ -37,7 +37,7 @@ sake of cross-platform.
    load_cifar10_dataset
    load_ptb_dataset
    load_matt_mahoney_text8_dataset
-   load_imbd_dataset
+   load_imdb_dataset
    load_nietzsche_dataset
    load_wmt_en_fr_dataset
 
@@ -79,7 +79,7 @@ Matt Mahoney's text8
 
 IMBD
 ^^^^^^^^^^^
-.. autofunction:: load_imbd_dataset
+.. autofunction:: load_imdb_dataset
 
 Nietzsche
 ^^^^^^^^^^^^^^